1. Field of the Invention
The present invention relates to a step-sliding type cutter knife which holds a blade slidable in the cutter knife body, and which allows the blade to step-wise slide out or in by operating the slider. More particularly, the invention pertains to an auto-locking and step-sliding type cutter knife, in which the blade is locked so as not to slide when an external force directly acts on the blade, whereas the blade can slide out or in under the operation by the slider.
2. Description of Related Techniques
In the fields of the auto-locking and step-sliding type cutter knife, the applicant of the present invention has already developed a cutter knife, capable of withstanding a large load directly acting on the blade, with a simple structure, to which a patent has been granted (Japanese Patent No. 2,059,272).
FIG. 1 shows a perspective view of the cutter knife, and FIG. 2 shows an exploded perspective view thereof. FIG. 3 shows a plan view of the locking mechanism of this cutter knife, and FIG. 4 shows a longitudinal sectional view of the locking mechanism, taken along a longitudinal axis. The cutter knife has a metallic elongated sleeve member 2, and a blade 1 slidably held in the sleeve member 2. The blade 1 is slid out of or into the cutter knife body by operating the slider 3.
The sleeve member 2 is formed by bending a metal sheet to have a lipped-groove, wherein walls 22 are extended from both sides of a slit 21 into the groove. Each of the walls 22 has a plurality of engagement indentations 23 formed thereon at regular intervals along the advancing or retracting direction of the blade 1. Each of the engagement indentations 23 has a pair of end walls 24, which face to each other in the advancing or retracting direction of the blade 1. A grip 4 of a synthetic resin is fixed to the sleeve member 2 by insert molding or the like.
As seen in the exploded perspective view shown in FIG. 2, the slider 3 comprises a slider body 5, an operating member 6, and a spring member 7 disposed between the slider body 5 and the operating member 6.
The slider body 5 is connected to the blade 1, and slides inside the sleeve member 2. The slider body 5 comprises a base portion 51 and a holder portion 52. The base portion 51 is slidably held between the base wall 25 (see FIG. 4) and the walls 22 of the sleeve member 2, and the holder portion 52 is raised from the base portion 51 to hold the operating member 6. The base portion 51 has a projection 53 at its one end, and the projection 53 is inserted into a connection hole 12 formed at one end of the blade 1 to thereby connect the slider body 5 to the blade 1 within the sleeve member 2.
On the other hand, the operating member 6 is so coupled with the slider body 5 as to be relatively movable to the body 5 in parallel to the sliding direction of the body 5, and is exposed to outside through the slit 21 of the sleeve member 2. The operating member 6 comprises an operating plate 61 having a plurality of anti-slip grooves 62 formed at its upper face, and a locking part 63 which is protruded from the underside of the operating plate 61 and is inserted into the opening 57 of the holder portion of the slider body 5. Claws 64 with widths narrower than the width of the groove 58 of the slider body 5 are formed on both side faces of the locking part 63 and are fitted in the groove 58 and engaged therewith. Thus, the operating member 6 can slide in the advancing or retracting direction of the blade 1, when coupled with the slider body 5.
The spring member 7 has a convex engagement head 72 which is urged into one of the engagement indentations 23 to thereby lock the sliding of the blade 1. The spring member 7 is held between slider body 5 and the operating member 6 in such the blade-locking state. The spring member 7 is formed by bending one metal sheet, so that the flat spring portion 71 with a narrow width which extends along the advancing or retracting direction of the blade 1 is formed integrally with the convex engagement head 72 which has a width wider than that of the spring portion 71 and which is raised from the center of the spring portion 71. The engagement head 72 is composed of a pair of flat faces 73 facing to each other, and a curved face 74 bridging the flat faces.
The base portion 51 of the slider body 5 has a wider central opening 54 (FIG. 4) for receiving the engagement head 72 of the spring member 7, and narrow side openings 55 which are formed at both sides of the central opening 54. The total length of the openings 55 is slightly shorter than the whole length of the spring portion 71 of the spring member 7. Further, a slit 56 communicating with the openings 55 is formed between the holder portion 52 and the base portion 51. The holder portion 52 has an opening 57 at its center, and grooves 58 at its both sides, which communicate with the opening 57.
A V-shaped sloped face 65 is formed on the lower end of the locking part 63 of the operating member 6. This sloped face 65 is in contact with the curved face 74 of the engagement head 72, when the spring member 7 is inserted into the slit 56 of the slider body 5 and coupled with the slider body 5 with its spring portion 71 held substantially flat without any bending.
When the operating member 6 of the slider is operated to slide the blade 1, the operating member 6 is moved relative to the slider body 5 so that the engagement head 72 of the spring member is pushed downward by the sloped face 65 of the operating member 6. As a result, the engagement head 72 is put outside the engagement indentation 23 to unlock the blade. On the other hand, when the engagement head 72 of the spring member is moved to another adjacent engagement indentation, the engagement head 72 is automatically pushed up into this another adjacent engagement indentation by the urging force of the spring member to thereby relock the sliding of the blade (auto-locking).
In the cutter knife constructed as above, the blade can be slid out of or into the cutter knife body by operating the slider. On the other hand, when an external force is directly applied on the blade, the sliding of the blade is inhibited by the action of the locking mechanism. Thus, such a disadvantage can be prevented that the blade is undesirably slid by an external force which acts on the blade from a subject being cut, during the cutting operation.
However, in some situations, the above auto-locking type cutter knife would be rather inconvenience to skilled workers. In many cases, after a cutting operation, the skilled workers push the blades against the hard surfaces of metal plates or the like, to thereby retract the blade inside the cutter knives. However, with the cutter knife constructed as above, even if the blade is pushed against the hard surface, the blade can not be retracted because of the auto-locking mechanism. Therefore, it is needed to operate the slider for retracting the blade inside the cutter knife body. The skilled workers feel this operation troublesome.